Bulletin of the American Physical Society
2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009; Denver, Colorado
Session J9: Top Mass |
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Sponsoring Units: DPF Chair: Kenneth Bloom, University of Nebraska-Lincoln Room: Governor's Square 11 |
Sunday, May 3, 2009 1:30PM - 1:42PM |
J9.00001: New Method For Extracting the Mass of the Top Quark From All-Jets Events Gianluca Petrillo Six-jet events, arising from decays of $t\bar{t}$ pairs in which both tops decay into a $W$ boson and a $b$ quark, and both $W$s decay into quark-antiquark pairs, constitute a potentially rich source of completely reconstructable top quarks for mass extraction analyses. However, even when two of the jets are tagged as originating from b-quarks, the mass analysis is complicated by uncertainties in assigning the four other jets to their originating partons when assembling the $\bar{t}t$ pairs. We introduce and describe a new top mass extraction technique that directly addresses this complication, and present preliminary results from applying this technique to data recorded by the D0 experiment at the Fermilab Tevatron. [Preview Abstract] |
Sunday, May 3, 2009 1:42PM - 1:54PM |
J9.00002: A matrix element analysis measurement of the top quark mass in the lepton + jets channel with an in situ jet energy scale measurement Daryl Hare We measure the top quark mass from $p\bar p$ collisions at 1.96 TeV at CDF in the lepton + jets channel with at least 3 $fb^{-1}$ of data. Events require a single lepton, missing transverse energy, and 4 jets of which at least one must be tagged as a b jet. We use a 2D unbinned likelihood fit based on per-event probabilities calculated from leading-order signal ($t\bar t$) and background ($W$+jets) matrix elements. Our measurement is dependent upon the energy scale of calorimeter jets, so we measure this scale in-situ by constraining the invariant mass of the two jets from to the W boson mass. [Preview Abstract] |
Sunday, May 3, 2009 1:54PM - 2:06PM |
J9.00003: Measurement of the Mass Difference between Top and Antitop Michael Wang We discuss a measurement of the mass difference ($\Delta_m$) between $t$ and $\overline{t}$ quarks in lepton+jets final states of $t\overline{t}$ events in data collected with the D0 detector at Fermilab's Tevatron. $\Delta_m$ is measured using the Matrix Element approach developed at D0. We report the most likely $\Delta_m$ and an upper limit on $\Delta_m$ at 95\% confidence. This is the first measurement of a mass difference between a quark and its antiquark. [Preview Abstract] |
Sunday, May 3, 2009 2:06PM - 2:18PM |
J9.00004: ABSTRACT WITHDRAWN |
Sunday, May 3, 2009 2:18PM - 2:30PM |
J9.00005: Measurement of the top quark mass using quantities that are independent of the jet energy scale Ford Garberson We will present two techniques for measuring the top quark mass in the lepton plus jets channel using quantities independent of the jet energy scale uncertainty. One technique exploits the correlation of the transverse decay length of $b$-tagged jets with the top mass, and the other exploits the correlation of the transverse momentum of the lepton in the same events with the top mass. While these results are still statistically limited, their precision will improve with added data at the Tevatron and the LHC. Further, since their correlation to more conventional top mass measurement techniques is small, they will help to reduce the overall uncertainty on the top mass in combination with other results. [Preview Abstract] |
Sunday, May 3, 2009 2:30PM - 2:42PM |
J9.00006: ABSTRACT WITHDRAWN |
Sunday, May 3, 2009 2:42PM - 2:54PM |
J9.00007: Top quark mass measurement in the lepton+jets and dilepton channels at CDF using $m_T$2 Jian Tang A measurement of top quark mass at CDF will be presented using a 3.0 $fb^{-1}$ data sample in both lepton+jets and dilepton channels. In the lepton+jets channel, we determine the reconstructed top quark mass by minimizing the $\chi^{2}$ for the overconstrained kinematic system, and we also measure the hadronically decaying $W$ boson mass to provide an $in-situ$ improvement in the determination of jet energy scale. In the dilepton channel, we replace our old observable $H_T$, which is the scalar sum of transverse energy of all particles in one event, with a new observable $m_T^2$, which is used in $W$ mass measurements and SUSY searches. We find a satisfying improvement in our result of top quark mass measurement using this new observable. [Preview Abstract] |
Sunday, May 3, 2009 2:54PM - 3:06PM |
J9.00008: Plans for Jet Energy Corrections at CMS Kalanand Mishra We present a plan for Jet Energy Corrections at CMS. Jet corrections at CMS will come initially from simulation tuned on test beam data, directly from collision data when available, and ultimately from a simulation tuned on collision data. The corrections will be factorized into a fixed sequence of sub-corrections associated with different detector and physics effects. The following three factors are minimum requirements for most analysis: offset corrections for pile-up and noise; correction for the response of the calorimeter as a function of jet pseudorapidity relative to the barrel; correction for the absolute response as a function of transverse momentum in the barrel. The required correction gives a jet Lorentz vector equivalent to the sum of particles in the jet cone emanating from a QCD hard collision. We discuss the status of these corrections, the planned data-driven techniques for their derivation, and their anticipated evolution with the stages of the CMS experiment. [Preview Abstract] |
Sunday, May 3, 2009 3:06PM - 3:18PM |
J9.00009: Background studies and spin correlation expectations in $t \bar t$ events in the $e\mu$ decay channel at the LHC Alaettin Serhan Mete One of the many interesting features of the top quark is its extraordinarily short lifetime. One consequence of this short lifetime is that the spin information of a decaying top quark is inherited by the decay products. Thus the spin information of the decaying top-antitop pairs can be extracted by examining the final state particles. A requisite step in such an analysis is the selection of a clean sample of $t\bar t \rightarrow e\mu$ events and this can be done by a careful examination of the background processes. We lay out a cut based method to enhance the signal versus the background in $t\bar t$ events in the $e\mu$ decay channel using Monte Carlo events and we also map out a method to investigate $t\bar t$ spin correlation at the ATLAS experiment at the LHC. [Preview Abstract] |
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